ASSEMBLY CONSTITUTING AN ACOUSTIC ABSORBENT MATERIAL

Abstract

ASSEMBLY CONSTITUTING AN ACOUSTIC ABSORBENT MATERIAL The invention relates to an assembly (100) constituting an acoustically absorbing material and comprising a first plate (102), a second plate (104) perforated with holes (106), an intermediate plate (110), a first honeycomb structure (112) comprising two first cages (120), a second honeycomb structure (114) comprising two second cages (122) aligned with the first cages (120), wherein the intermediate plate (110) is perforated with a through hole (132) and for each first cage (120), a tube (130) opening at both ends, wherein one end of said tube (130) is fixed to said intermediate plate (110) at the through hole (132) associated with said first cage (120), wherein the other end of said tube (130) is inside said first cage (120) and where the two tubes (130) are of different inner diameter and length.Such an assembly provides broadband attenuation and is easy to manufacture. Fig. 1.

Description

Title of the invention: ASSEMBLY CONSTITUTING AN ACOUSTIC ABSORBENT MATERIAL Technical field

[0001] The present invention relates to an assembly constituting an acoustically absorbing material. PREVIOUS STATE OF THE ART

[0002] During its operation, an aircraft engine generates noise. This engine is housed in a nacelle, and to reduce this noise, it is known to install assemblies constituting an acoustically absorbing material around the engine in the nacelle structure.

[0003] Such assemblies constituting an acoustically absorbing material take, for example, the form of honeycomb structures. Such a honeycomb structure comprises two parallel plates, one of which is perforated, and between which hexagonal cells are arranged juxtaposed to one another.

[0004] Although such assemblies give good results from an acoustic point of view, it is desirable to find an assembly constituting an acoustically absorbing material that allows attenuation of a wider range of acoustic frequencies. Description of the invention

[0005] An object of the present invention is to provide an assembly constituting an acoustically absorbing material which can attenuate several acoustic frequencies, and in particular both low and high frequencies.

[0006] To this end, an assembly is proposed that constitutes an acoustically absorbent material and comprises:

[0007] - a first plate,

[0008] - a second plate pierced with holes,

[0009] - an intermediate plate,

[0010] - a first honeycomb structure comprising two first cages extending between the first plate and the intermediate plate,

[0011] - a second honeycomb structure comprising two second cages extending between the second plate and the intermediate plate, where for each first cage, a second cage is aligned with said first cage, and the intermediate plate is pierced with a through hole between said first cage and the associated second cage, and

[0012] - for each second cage, a tube opening at both ends, where one end of said tube is fixed to said intermediate plate at the through hole associated with said second cage, where the other end of said tube is inside said second cage and where the two tubes are of different internal diameter and length.

[0013] Such an assembly makes it possible to obtain broadband attenuation.

[0014] The invention also proposes an assembly comprising two sets according to the previous variant where the two sets are joined together and where the four tubes are all of different internal diameter and length.

[0015] The invention also proposes an assembly comprising a set according to the preceding variant and a sub-assembly attached to said set and constituting an acoustically absorbing material and comprising:

[0016] - a first sub-plate,

[0017] - a second sub-plate pierced with holes,

[0018] - an intermediate sub-plate,

[0019] - a first honeycomb substructure comprising two first cages extending between the first sub-plate and the intermediate sub-plate,

[0020] - a second honeycomb substructure comprising two second cages extending between the second sub-plate and the intermediate sub-plate, where for each first cage, a second cage is aligned with said first cage, where for a second cage, the intermediate sub-plate is pierced with a through hole between said second cage and the associated first cage, and where for the other second cage, the intermediate plate is pierced with several through holes between said second cage and the associated first cage, and

[0021] - for said a second cage, a tube opening at both ends, where one end of said tube is fixed to said intermediate sub-plate at the through hole associated with said second cage, where the other end of said tube is inside said second cage and where said tube is of different internal diameter and length from those of the tubes of said assembly.

[0022] The invention also proposes an assembly comprising a set according to the preceding variant and a sub-assembly attached to said set and constituting an acoustically absorbing material and comprising:

[0023] - a first sub-plate,

[0024] - a second sub-plate pierced with holes,

[0025] - an intermediate sub-plate,

[0026] - a first honeycomb substructure comprising two first cages extending between the first sub-plate and the intermediate sub-plate,

[0027] - a second honeycomb substructure comprising two second cages extending between the second sub-plate and the intermediate sub-plate, where for each first cage, a second cage is aligned with said first cage, where for a second cage, the intermediate sub-plate is pierced with a through hole between said second cage and the associated first cage, and where for the other second cage, the intermediate plate is pierced with a through hole between said second cage and the associated first cage, where said through hole is the same internal dimensions as the cages, and

[0028] - for said a second cage, a tube opening at both ends, where one end of said tube is fixed to said intermediate sub-plate at the through hole associated with said second cage, where the other end of said tube is inside said second cage and where said tube is of different internal diameter and length from those of the tubes of said assembly.

[0029] The invention also proposes an assembly comprising a set according to the preceding variant and a sub-assembly attached to said set and constituting an acoustically absorbing material and comprising:

[0030] - a first sub-plate,

[0031] - a second sub-plate pierced with holes,

[0032] - an intermediate sub-plate,

[0033] - a first honeycomb substructure comprising two first cages extending between the first sub-plate and the intermediate sub-plate,

[0034] - a second honeycomb substructure comprising two second cages extending between the second sub-plate and the intermediate sub-plate, where for each first cage, a second cage is aligned with said first cage, where for one second cage, the intermediate sub-plate is pierced with a through hole between said first cage and the associated second cage, and where for the other second cage, the intermediate plate is solid between said first cage and the associated second cage, and

[0035] - for said a second cage, a tube opening at both ends, where one end of said tube is fixed to said intermediate sub-plate at the through hole associated with said second cage, where the other end of said tube is inside said second cage and where said tube is of different internal diameter and length from those of the tubes of said assembly.

[0036] Advantageously, the internal volumes of each tube are equal.

[0037] Advantageously, the internal volumes of each tube are different.

[0038] Advantageously, between two tubes, the ratio of the tube lengths is between 0.5 and 2, and the ratio of the tube inner diameters is between 0.1 and 4.

[0039] Advantageously, for a first tube, the length is between 11 mm and 15 mm and the inner diameter is between 0.8 mm and 2.8 mm, for a second tube, the length is between 8 mm and 12 mm and the inner diameter is between 1.0 mm and 3.0 mm, and for a third tube, the length is between 7 mm and 11 mm and the inner diameter is between 1.5 mm and 3.5 mm.

[0040] Advantageously, for a fourth tube, the length is between 6 mm and 10 mm or between 5 mm and 9 mm and the inner diameter is respectively between 3.0 mm and 7.8 mm or between 4.0 mm and 6.0 mm. Brief description of the drawings

[0041] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0042] [Fig-1] is a cross-sectional and exploded view of an assembly constituting an acoustically absorbing material according to the invention,

[0043] [Fig.2] is a cross-sectional view of an assembly according to a first embodiment of the invention,

[0044] [Fig.3] is a cross-sectional view of an assembly according to a second embodiment of the invention,

[0045] [Fig.4] is a cross-sectional view of an assembly according to a third embodiment of the invention, and

[0046] [Fig.5] is a cross-sectional view of an assembly according to a fourth embodiment of the invention.

[0047] DETAILED STATEMENT OF EMBODIMENT METHODS

[0048] Figure 1 shows an assembly 100 constituting an acoustically absorbing material according to the invention. The assembly 100 comprises a first plate 102 and a second plate 104 which are spaced apart. One of the plates, here the second plate 104, is perforated with holes 106 which pass through it to allow the passage of acoustic waves.

[0049] Between the first plate 102 and the second plate 104, an intermediate plate 110 is arranged. The three plates 102, 104 and 110 are parallel.

[0050] Between the first plate 102 and the intermediate plate 110, there extends a first honeycomb structure 112 and between the second plate 104 and the intermediate plate 110, there extends a second honeycomb structure 114.

[0051] Thus, according to a stacking direction 50, the assembly 100 successively comprises the first plate 102, the first honeycomb structure 112, the intermediate plate 110, the second honeycomb structure 114 and the second plate 104.

[0052] The first structure 112 comprises two first cages 120, where each first cage 120 is hollow and delimited by walls 124 extending in planes parallel to the stacking direction 50. Preferably, each first cage 120 delimits a hexagonal cell, but other shapes are conceivable. The two first cages 120 are joined to each other along a common wall 124.

[0053] Similarly, the second structure 114 comprises two second cages 122, where each second cage 124 is hollow and delimited by walls 126 extending in planes parallel to the stacking direction 50. Preferably, each second cage 124 delimits a hexagonal cell, but other shapes are conceivable. The two second cages 122 are joined to each other along a wall 126.

[0054] For each first cage 120, a second cage 122 is aligned with the first cage 120. This alignment of the first and second cages 120, 122 is carried out within manufacturing tolerances: a misalignment of less than 5% may appear between a first cage 120 and a second cage 122. For each first cage 120, the intermediate plate 110 is drilled with a through hole 132 which extends between the first cage 120 and the associated second cage 122 so as to ensure a passage between the cages 120 and 122.

[0055] The first plate 102 and the first structure 112 are fixed to each other for example by gluing, welding, etc.

[0056] The second plate 104 and the second structure 114 are fixed to each other for example by gluing, welding, etc.

[0057] The first structure 112 and the intermediate plate 110 are fixed to each other for example by gluing, welding, etc.

[0058] The second structure 114 and the intermediate plate 110 are fixed to each other for example by gluing, welding, etc.

[0059] The first structure 112, together with the first plate 102 and the intermediate plate 110, forms a quarter-wave resonator that attenuates high acoustic frequencies. The assembly 100 thus provides broadband attenuation and is easy to manufacture.

[0060] The assembly 100 also includes, for each second cage 122, a tube 130 opening at both ends and extending in a direction parallel to the stacking direction 50.

[0061] One end of each tube 130 is fixed to the intermediate plate 110 at the through hole 132 associated with the second cage 122. Thus fluidic continuity between the second cage 122 and the first cage 120 via the tube 130. The fixing of the tubes 130 to the intermediate plate 110 is carried out for example by welding, gluing, etc.

[0062] The other end of each tube 130 is inside the second cage 122 and opens into it.

[0063] The second structure 114, with the second plate 104, the intermediate plate 110 and the tubes 130 form a Helmholtz resonator which attenuates low acoustic frequencies.

[0064] To attenuate several frequencies, the two tubes 130 have different inner diameters and lengths.

[0065] Thus, with such assemblies 100 comprising tubes 130 of different internal diameter and length and by combining them, it is possible to attenuate many acoustic frequencies according to the needs.

[0066] The manufacturing process for such an assembly comprises the following steps, carried out successively:

[0067] - the second structure 114 is fixed to the second plate 104, so that The second plate 104 closes off a so-called upper face of the second cages 122 of the second structure 114,

[0068] - the intermediate plate 110 is fixed to the second structure 114 (already assembled to the second plate 104), so that the intermediate plate 110 closes a so-called lower face of the second cages 122 of the second structure 114, where the intermediate plate 110 is not pierced with through holes and is therefore a solid plate,

[0069] - the tubes 130 are inserted into the intermediate plate 110, from the face of the intermediate plate 110 which is opposite the one which is fixed to the second structure 114, so as to pierce and pass through the intermediate plate 110 to emerge into the second cages 122 of the second structure 114,

[0070] - the first structure 112 is fixed to the intermediate plate 110, so that that the intermediate plate 110 closes a so-called upper face of the first cages 120 of the first structure 112, and

[0071] - the first plate 102 (rigid) is fixed to the first structure 112 (already assembled to the intermediate plate 110) so that the first plate 102 closes a so-called lower face of the first cages 120 of the first structure 112.

[0072] Figure 2 shows an assembly 200 of two sets 100 which are joined together along a wall 126 which is common to both sets 100. In the embodiment shown here, the first four cages 120, and therefore the second four cages 122, are aligned in the same direction, thus forming a online structure, but it is possible to predict that the two sets of 100 are next to each other in such a way as to form a 2 over 2 cubic structure.

[0073] In this assembly 200, the four tubes 130 are all of different inner diameter and length.

[0074] In this assembly 200, the first plate 102 is common to both sets 100 and in the same way, the second plate 104 and the intermediate plate 110 are also common to both sets 100. The two sets 100 can thus be formed at the same time to constitute the assembly 200.

[0075] Fig. 3 shows an assembly 300 of an assembly 100 which is attached to a sub-assembly 350 which also constitutes an acoustically absorbing material.

[0076] The sub-assembly 350 has overall the same structure as the assembly 100 and it comprises a first sub-plate 352, a second sub-plate 354 with holes 306 and an intermediate sub-plate 310 between the first sub-plate 352 and the second sub-plate 354.

[0077] The subassembly 350 comprises a first honeycomb substructure 312 comprising two first cages 320 between the first sub-plate 352 and the intermediate sub-plate 310 and a second honeycomb substructure 314 comprising two second cages 322 between the second sub-plate 354 and the intermediate sub-plate 310.

[0078] For each first cage 320 of the subset 350, a second cage 322 of the subset 350 is aligned with the first cage 320.

[0079] For one of the second cages 322 of the subassembly 350, the intermediate sub-plate 310 has a through hole 332 drilled between the second cage 322 and the associated first cage 320. For this second cage 322, a tube 330 with two open ends is installed. The tube 330 is fixed at one end to the intermediate sub-plate 310 at the through hole 332 associated with the second cage 322, and the other end of the tube 330 is inside the second cage 322.

[0080] The tube 330 of sub-assembly 350 has a different inner diameter and length than the tubes 130 of assembly 100.

[0081] In addition, for the other second cage 322 of the subassembly 350, the intermediate plate 310 is pierced with several through holes 332a between said second cage 322 and the associated first cage 320.

[0082] As with assembly 100, the first cages 320 and the second cages 322 of subassembly 350 are hollow and delimited by walls 324 and 326 respectively. The first two cages 320 of subassembly 350 are joined along a common wall 324 and the second cages 322 of subassembly 350 are joined along a common wall 323.

[0083] The subset 350 and the set 100 are joined along a common wall 124, 126, 324, 326.

[0084] In the embodiment shown here, the first four cages 120 and 320, and therefore the second four cages 122 and 322, are aligned in the same direction, thus forming a line structure, but it is possible to provide that the set 100 and the subset 350 are next to each other so as to form a 2 on 2 cubic structure.

[0085] In this assembly 300, the first plate 102 and the first sub-plate 352 are common to the assembly 100 and the sub-assembly 300 and in the same way, the second plate 104 and the second sub-plate 354, on the one hand, and the intermediate plate 110 and the intermediate sub-plate 310, on the other hand, are also common to the assembly 100 and the sub-assembly 300.

[0086] Fig. 4 shows an assembly 400 of an assembly 100 which is attached to a sub-assembly 450 which also constitutes an acoustically absorbing material.

[0087] The sub-assembly 450 has overall the same structure as the assembly 100 and it comprises a first sub-plate 452, a second sub-plate 454 with holes 406 and an intermediate sub-plate 410 between the first sub-plate 452 and the second sub-plate 454.

[0088] The subassembly 450 comprises a first honeycomb substructure 412 comprising two first cages 420 between the first sub-plate 452 and the intermediate sub-plate 410 and a second honeycomb substructure 414 comprising two second cages 422 between the second sub-plate 454 and the intermediate sub-plate 410.

[0089] For each first cage 420 of the subassembly 450, a second cage 422 of the subassembly 450 is aligned with the first cage 420.

[0090] For one of the second cages 422 of the subassembly 450, the intermediate sub-plate 410 has a through hole 432 drilled between the second cage 422 and the associated first cage 420. For this second cage 422, a tube 430 with two open ends is installed. The tube 430 is fixed at one end to the intermediate sub-plate 410 at the through hole 432 associated with the second cage 422, and the other end of the tube 430 is inside the second cage 422.

[0091] The tube 430 of subassembly 450 has a different internal diameter and length than the tubes 130 of assembly 100.

[0092] Furthermore, for the other second cage 422 of the subassembly 450, the intermediate plate 410 is pierced with a through hole 432a between said second cage 422 and the associated first cage 420, and the through hole 432a is of the dimensions internal cages 420 and 422 are associated, that is to say there is no intermediate plate 410 between them and they then form a single cage over the entire height.

[0093] As with assembly 100, the first cages 420 and the second cages 422 of subassembly 450 are hollow and delimited by walls 424 and 426 respectively. The first two cages 420 of subassembly 450 are joined along a common wall 424 and the second cages 422 of subassembly 450 are joined along a common wall 423.

[0094] The subset 450 and the set 100 are joined along a common wall 124, 126, 424, 426.

[0095] In the embodiment shown here, the first four cages 120 and 420, and therefore the second four cages 122 and 422, are aligned in the same direction, thus forming a line structure, but it is possible to provide that the set 100 and the subset 450 are next to each other so as to form a 2 on 2 cubic structure.

[0096] In this assembly 400, the first plate 102 and the first sub-plate 452 are common to the assembly 100 and the sub-assembly 400 and in the same way, the second plate 104 and the second sub-plate 454, on the one hand, and the intermediate plate 110 and the intermediate sub-plate 410, on the other hand, are also common to the assembly 100 and the sub-assembly 400.

[0097] Fig. 5 shows an assembly 500 of an assembly 100 which is attached to a sub-assembly 550 which also constitutes an acoustically absorbing material.

[0098] The sub-assembly 550 has overall the same structure as the assembly 100 and it comprises a first sub-plate 552, a second sub-plate 554 with holes 506 and an intermediate sub-plate 510 between the first sub-plate 552 and the second sub-plate 554.

[0099] The subassembly 550 comprises a first honeycomb substructure 512 having two first cages 520 between the first sub-plate 552 and the intermediate sub-plate 510 and a second honeycomb substructure 514 having two second cages 522 between the second sub-plate 554 and the intermediate sub-plate 510.

[0100] For each first cage 520 of the subset 550, a second cage 522 of the subset 550 is aligned with the first cage 520.

[0101] For one of the second cages 522 of the subassembly 550, the intermediate sub-plate 510 is drilled with a through hole 532 between the second cage 522 and the associated first cage 520. For this second cage 522, a tube 530 with openings at both ends is installed. The tube 530 is fixed at one end to the intermediate sub-plate 510 at the level of the associated through hole 532. to the second cage 522 considered and the other end of the tube 530 is inside said second cage 522 considered.

[0102] The tube 530 of subassembly 550 has a different internal diameter and length than the tubes 130 of assembly 100.

[0103] Furthermore, for the other second cage 522 of the subassembly 550, the intermediate plate 510 is solid, that is, unperforated between said second cage 522 and the associated first cage 520. In other words, no tube is inserted into the intermediate plate 510 at the level of this other second cage 522, so that it has no through hole.

[0104] As with assembly 100, the first cages 520 and the second cages 522 of subassembly 550 are hollow and delimited by walls 524 and 526 respectively. The first two cages 520 of subassembly 550 are joined along a common wall 524 and the second cages 522 of subassembly 550 are joined along a common wall 523.

[0105] The subset 550 and the set 100 are joined along a common wall 124, 126, 524, 526.

[0106] In the embodiment shown here, the first four cages 120 and 520, and therefore the second four cages 122 and 522, are aligned in the same direction, thus forming a line structure, but it is possible to provide that the set 100 and the subset 550 are next to each other so as to form a 2 on 2 cubic structure.

[0107] In this assembly 500, the first plate 102 and the first sub-plate 552 are common to the assembly 100 and the sub-assembly 500 and in the same way, the second plate 104 and the second sub-plate 554, on the one hand, and the intermediate plate 110 and the intermediate sub-plate 510, on the other hand, are also common to the assembly 100 and the sub-assembly 500.

[0108] The different assemblies 200, 300, 400, 500 described above allow the acoustic frequencies to be attenuated to be chosen and several of these assemblies can then be put in place in different parts of an aircraft to attenuate the noises generated.

[0109] For each of the embodiments described above, it is possible to provide that the internal volumes of each tube 130, 330, 430, 530 are equal.

[0110] For each of the embodiments described above, it is also possible to provide that the internal volumes of each tube 130, 330, 430, 530 are different, i.e. vary from one tube to another.

[0111] According to a particular embodiment, in the various assemblies 200, 300, 400, 500 described above, it is preferably provided that the ratio of the lengths of the tubes 130, 330, 430, 530 is between 0.5 and 2, and that the ratio of the internal diameters of the tubes 130, 330, 430, 530 is between 0.1 and 4.

[0112] According to a particular arrangement concerning each of the assemblies 200, 300, 400, 500 described above, for a first tube 130, 330, 430, 530, the length of said first tube 130, 330, 430, 530 is between 11 mm and 15 mm and for example equal to 13 mm and the inside diameter of said first tube 130, 330, 430, 530 is between 0.8 mm and 2.8 mm and for example equal to 1.8 mm, for a second tube 130, 330, 430, 530, the length of said second tube 130, 330, 430, 530 is between 8 mm and 12 mm and for example equal to 10 mm and the inside diameter of said second tube 130, 330, 430, 530 is between 1.0 mm and 3.0 mm and for example equal to 2.0 mm, and for a third tube 130, 330, 430, 530, the length of said third tube 130, 330, 430, 530 is between 7 mm and 11 mm and for example equal to 9 mm and the inner diameter of said third tube 130, 330, 430, 530 is between 1.5 mm and 3.5 mm and for example equal to 2.5 mm.

[0113] In the assembly 200 according to the first embodiment, for a fourth tube 130, the length of said fourth tube 130 is between 6 mm and 10 mm or between 5 mm and 9 mm and is for example equal to 8 mm or 8 mm or 7 mm and the internal diameter of said fourth tube 130 is then respectively between 3.0 mm and 7.8 mm or between 4.0 mm and 6.0 mm and is equal for example respectively to 4.0 mm or 6.8 mm or 5.0 mm.

[0114] This particular arrangement is more particularly provided for in the case of cages with regular hexagonal sections of 9.525 mm on each side with cage heights of the order of 14 mm for the second structure 114, 314, 414, 514 and of the order of 25 mm for the first structure 112, 312, 412, 512.

[0115] The various elements constituting the assembly 100 and the various assemblies 200, 300, 400, 500 can be made of different materials such as, for example, metallic materials like aluminum or an aluminum alloy, or composite materials. The method of fastening the elements together will also depend on the materials used.

Claims

Demands

1. An assembly (100) constituting an acoustically absorbing material and comprising: - a first plate (102), - a second plate (104) perforated with holes (106), - an intermediate plate (110), - a first honeycomb structure (112) comprising two first cages (120) extending between the first plate (102) and the intermediate plate (110), - a second honeycomb structure (114) comprising two second cages (122) extending between the second plate (104) and the intermediate plate (110), wherein for each first cage (120), a second cage (122) is aligned with said first cage (120) and the intermediate plate (110) is perforated with a through hole (132) between said first cage (120) and the associated second cage (122), and - for each second cage (122), a tube (130) opening at both ends,where one end of said tube (130) is fixed to said intermediate plate (110) at the through hole (132) associated with said second cage (122), where the other end of said tube (130) is inside said second cage (122), and where the two tubes (130) have different internal diameters and lengths.

2. Assembly (200) comprising two sets (100) according to claim 1, wherein the two sets (100) are joined together and wherein the four tubes (130) are all of different inner diameter and length.

3. Assembly (300) comprising an assembly (100) according to claim 1, and a sub-assembly (350) attached to said assembly (100) and constituting an acoustically absorbing material and comprising: - a first sub-plate (352), - a second sub-plate (354) perforated with holes (306), - an intermediate sub-plate (310), - a first honeycomb substructure (312) comprising two first cages (320) extending between the first sub-plate (352) and the intermediate sub-plate (310),

4. - a second honeycomb substructure (314) comprising two second cages (322) extending between the second sub-plate (354) and the intermediate sub-plate (310), wherein for each first cage (320), a second cage (322) is aligned with said first cage (320), wherein for one second cage (322), the intermediate sub-plate (310) is pierced with a through hole (332) between said second cage (322) and the associated first cage (320), and wherein for the other second cage (322), the intermediate plate (310) is pierced with several through holes (332a) between said second cage (322) and the associated first cage (320), and - for said second cage (322), a tube (330) opening at both ends, wherein one end of said tube (330) is fixed to said intermediate sub-plate (310) at the through hole (332) associated with said second cage (322), wherein the other end of said tube (330) is inside said second cage (322), and wherein said tube (330) has an internal diameter and length different from those of the tubes (130) of said assembly (100). Assembly (400) comprising an assembly (100) according to claim 1, and a sub-assembly (450) attached to said assembly (100) and constituting an acoustically absorbing material and comprising: - a first sub-plate (452), - a second sub-plate (454) pierced with holes (406), - an intermediate sub-plate (410), - a first honeycomb substructure (412) comprising two first cages (420) extending between the first sub-plate (452) and the intermediate sub-plate (410), - a second honeycomb substructure (414) comprising two second cages (422) extending between the second sub-plate (454) and the intermediate sub-plate (410), wherein for each first cage (420), a second cage (422) is aligned with said first cage (420), wherein for one second cage (422), the intermediate sub-plate (410) is pierced with a through hole (432) between said second cage (422) and the associated first cage (420), and wherein for the other second cage (422), the intermediate plate (410) is pierced with a through hole (432a) between said second cage (422) and the associated first cage (420), wherein said through hole (432a) has the internal dimensions of the cages (420, 422), and - for said second cage (422), a tube (430) opening at both ends, where one end of said tube (430) is fixed to said intermediate sub-plate (410) at the level of the through hole (432) associated with said second cage (422), where the other end of said tube (430) is inside said second cage (422) and where said tube (430) has an internal diameter and length different from those of the tubes (130) of said assembly (100).

5. Assembly (500) comprising an assembly (100) according to claim 1, and a subassembly (550) attached to said assembly (100) and constituting an acoustically absorbing material and comprising: - a first sub-plate (552), - a second sub-plate (554) perforated with holes (506), - an intermediate sub-plate (510), - a first honeycomb substructure (512) comprising two first cages (520) extending between the first sub-plate (552) and the intermediate sub-plate (510), - a second honeycomb substructure (514) comprising two second cages (522) extending between the second sub-plate (554) and the intermediate sub-plate (510), wherein for each first cage (520), a second cage (522) is aligned with said first cage (520), where, for a second cage (522), the intermediate sub-plate (510) is pierced with a through hole (532) between said second cage (522) and the associated first cage (520),and where, for the other second cage (520), the intermediate plate (510) is solid between said second cage (522) and the associated first cage (520), and - for said second cage (522), a tube (330) opening at both ends, where one end of said tube (530) is fixed to said intermediate sub-plate (510) at the through hole (532) associated with said second cage (522), where the other end of said tube (530) is inside said second cage (522), and where said tube (530) has a different internal diameter and length than the tubes (130) of said assembly (100).

6. Assembly (200, 300, 400, 500) according to any one of claims 2 to 5, characterized in that the internal volumes of each tube (130, 330, 430, 530) are equal.

7. Assembly (200, 300, 400, 500) according to any one of claims 2 to 5, characterized in that the internal volumes of each tube (130, 330, 430, 530) are different.

8. Assembly (200, 300, 400, 500) according to any one of claims 2 to 7, characterized in that between two tubes (130, 330, 430, 530), the ratio of the lengths of the tubes (130, 330, 430, 530) is between 0.5 and 2, and in that the ratio of the internal diameters of the tubes (130, 330, 430, 530) is between 0.1 and 4.

9. Assembly (200, 300, 400, 500) according to claim 8, characterized in that for a first tube (130, 330, 430, 530), the length is between 11 mm and 15 mm and the inner diameter is between 0.8 mm and 2.8 mm, in that for a second tube (130, 330, 430, 530), the length is between 8 mm and 12 mm and the inner diameter is between 1.0 mm and 3.0 mm, and in that for a third tube (130, 330, 430, 530), the length is between 7 mm and 11 mm and the inner diameter is between 1.5 mm and 3.5 mm.

10. Assembly (200) according to claim 9, characterized in that for a fourth tube (130), the length is between 6 mm and 10 mm or between 5 mm and 9 mm and the inner diameter is respectively between 3.0 mm and 7.8 mm or between 4.0 mm and 6.0 mm.

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